API interaction scripts in Bash Scripting - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of this curl command?

You run this command to get JSON data from a public API:

curl -s https://api.agify.io?name=michael | jq '.age'

What will be the output?

Bash Scripting

curl -s https://api.agify.io?name=michael | jq '.age'

A Returns an error because jq is not installed

B Returns the entire JSON response as a string

C Returns the predicted age as a number, e.g., 69

D Returns the name field from the JSON

💡 Hint

jq extracts specific fields from JSON output.

The command fetches JSON data about the name 'michael' and jq extracts the 'age' field, which is a number.

📝 Syntax

intermediate

Which curl command correctly sends JSON data via POST?

You want to send JSON data '{"name":"Alice"}' to an API endpoint using curl. Which command is correct?

A curl -X POST -d '{"name":"Alice"}' https://example.com/api

B curl -X POST -H 'Content-Type: application/json' -d '{"name":"Alice"}' https://example.com/api

C curl -X POST -H 'Content-Type: text/plain' -d '{"name":"Alice"}' https://example.com/api

D curl -X GET -H 'Content-Type: application/json' -d '{"name":"Alice"}' https://example.com/api

💡 Hint

APIs expect the Content-Type header to match the data format.

To send JSON data, you must set the Content-Type header to application/json and use POST method.

🔧 Debug

advanced

Why does this bash script fail to parse JSON correctly?

This script tries to get the 'token' field from an API response:

response=$(curl -s https://example.com/api/login)
token=$(echo "$response" | jq '.token')

But token is empty. Why?

Bash Scripting

response=$(curl -s https://example.com/api/login)
token=$(echo "$response" | jq '.token')

A Because curl needs -X POST to get a token

B Because jq cannot parse JSON from curl output

C Because the API does not return a token field

D Because $response is not quoted, so echo splits it and jq gets invalid input

💡 Hint

Think about how bash handles variables with spaces or newlines.

Without quotes, $response loses its JSON structure when passed to echo, causing jq to fail.

🚀 Application

advanced

How to extract all user IDs from a paginated API using bash?

An API returns user data in pages. Each page has a 'users' array and a 'next_page' URL or null if last page.

Write a bash approach to collect all user IDs from all pages.

A Use a loop that fetches each page URL, extracts user IDs, appends them, and follows 'next_page' until null

B Fetch only the first page and extract user IDs, ignoring pagination

C Use curl with -L to follow redirects and get all pages automatically

D Use jq to merge all pages by calling the API once with a large limit parameter

💡 Hint

Pagination requires multiple requests following the next page links.

You must loop through pages, extract IDs, and continue until no next page is given.

🧠 Conceptual

expert

What is the main risk of using curl with user input in a bash script?

You write a bash script that takes a URL from user input and runs:

curl "$user_url"

What is the biggest security risk here?

A User input could contain malicious commands causing command injection

B curl might download large files and fill disk space

C curl might fail if the URL is malformed

D User input might cause curl to connect to unsafe servers

💡 Hint

Think about how bash interprets variables and special characters.

If user input is not sanitized, it can inject commands or options that run unintended code.